Harbor Freight Jack - Heads up

[Roscoe]

Here is a thread from the BMW forum. The jack failure has to do with the protrusions on the lifting plate. Someone had the weight of the car on one of these points and it snapped. Reading the thread further suggested using a larger pad, piece of wood or even an actual hockey puck.

Roscoe

Here is is:

#6. Re: Harbor Freight lightweight jack failure - from Neil MallerTopDate: Wed, 21 Aug 2002 12:21:50 -0500
From: Neil Maller
Subject: Re: Harbor Freight lightweight jack failure

on 8/21/02 9:51 AM, Steve Lilley wrote:

> I just received my $189 jack yesterday. I'm pretty sure problems
> like the one described below can be avoided with only a couple
> dollars worth of material...
>
> Since the vertical fingers are slightly higher than the rubber pad,
> they carry all the weight when jacking a flat area of the car. In
> order to avoid this, I remove the rubber pad entirely and replace
> it with a 3/8" or 1/2" thick piece of wood cut into a circle. (I'm
> not sure what kind of wood it is, but it's really hard. Maybe oak
> or cherry?) Now the lifting load is always carried by the center
> of the jack pad, not the fingers on the edge. All the fingers do
> now is keep the wood circle in place.
>
>> I wondered how long these things would last. Ours is less than
>> 2 weeks old. Part of the weight of the car was resting on one of
>> the four vertical "fingers" surrounding the rubber pad. The
>> finger broke clear off taking about 20% of the circular aluminum
>> pad with it..

Most steel jacks have these fingers, presumably as a safety feature to
prevent a car's underside from sliding off the jack saddle.

However I think that's a design flaw for any aluminum jack. It's easy to see
how the jack could be positioned such that much of the car's weight was
being carried on one finger. Not only would this put a lot of force on the
finger, but it would also apply a large bending moment to the central mount.
Aluminum isn't that strong a material, and unless the saddle were made very
massive it would be at risk of breakage.

The other racing jacks I've seen either have a heavy continuous rim around
the saddle, or just have a couple of small notches. Both approaches strike
me as stronger then the HF jack design. However if the HF saddle is
positioned squarely on the E36 lifting puck, or otherwise on a flat surface,
then I think risk of breakage would probably be eliminated.